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| United States Patent |
6,235,858
|
|
Swarup
, et al.
|
May 22, 2001
|
Aminoplast curable film-forming compositions providing films having
resistance to acid etching
Abstract
An aminoplast-curable film-forming composition is disclosed. The
film-forming composition is a crosslinkable composition comprising (1) a
material containing a plurality of carbamate and/or urea functional groups
and (2) an aminoplast crosslinking agent. The composition provides a
coating with improved acid etch resistance, making the coating
particularly useful as an automotive clear coat.
| Inventors:
|
Swarup; Shanti (Allison Park, PA);
McCollum; Gregory J. (Gibsonia, PA);
Singer; Debra L. (Wexford, PA)
|
| Assignee:
|
PPG Industries Ohio, Inc. (Cleveland, OH)
|
| Appl. No.:
|
071174 |
| Filed:
|
May 1, 1998 |
| Current U.S. Class: |
526/301; 427/388.3; 526/302 |
| Intern'l Class: |
C08F 026/02 |
| Field of Search: |
427/388.3
526/301,302
|
References Cited
U.S. Patent Documents
| 2734891 | Feb., 1956 | Melamed | 528/259.
|
| 2806840 | Sep., 1957 | Aycock et al. | 526/288.
|
| 2923691 | Feb., 1960 | Young et al. | 528/259.
|
| 3014042 | Dec., 1961 | Mantz | 548/324.
|
| 3360504 | Dec., 1967 | Kelley | 526/288.
|
| 3369008 | Feb., 1968 | Hurwitz | 526/263.
|
| 3464328 | Sep., 1969 | Nordstrom | 525/159.
|
| 3479328 | Nov., 1969 | Nordstrom | 526/312.
|
| 3509085 | Apr., 1970 | Sekmakas | 524/9.
|
| 3563957 | Feb., 1971 | Beebe | 522/50.
|
| 3597380 | Aug., 1971 | Bertini et al. | 524/843.
|
| 3674838 | Jul., 1972 | Nordstrom | 260/482.
|
| 3773736 | Nov., 1973 | Williams et al. | 528/259.
|
| 3901936 | Aug., 1975 | Boroschewski | 560/29.
|
| 3922447 | Nov., 1975 | Isaksen et al. | 428/458.
|
| 3959202 | May., 1976 | Blank | 524/512.
|
| 4151142 | Apr., 1979 | Herman | 524/530.
|
| 4255570 | Mar., 1981 | Grogler et al. | 544/197.
|
| 4279833 | Jul., 1981 | Culbertson et al. | 560/115.
|
| 4361594 | Nov., 1982 | Winterbottom | 427/27.
|
| 4384102 | May., 1983 | Rasshofer et al. | 528/73.
|
| 4411951 | Oct., 1983 | Barsotti | 428/328.
|
| 4435559 | Mar., 1984 | Valko | 528/73.
|
| 4451597 | May., 1984 | Victorius | 524/39.
|
| 4455331 | Jun., 1984 | Barsotti | 428/446.
|
| 4520167 | May., 1985 | Blank et al. | 525/131.
|
| 4533716 | Aug., 1985 | Okoshi et al. | 528/73.
|
| 4543276 | Sep., 1985 | Parekh | 427/388.
|
| 4677168 | Jun., 1987 | Hoy et al. | 525/441.
|
| 4704442 | Nov., 1987 | Just et al. | 526/273.
|
| 4708984 | Nov., 1987 | Forgione et al. | 525/127.
|
| 4710542 | Dec., 1987 | Forgione et al. | 525/127.
|
| 4812506 | Mar., 1989 | Gilmore et al. | 524/512.
|
| 4837278 | Jun., 1989 | Cameron et al. | 525/162.
|
| 5039759 | Aug., 1991 | Hoy et al. | 525/437.
|
| 5093414 | Mar., 1992 | Rauterkus et al. | 524/813.
|
| 5115015 | May., 1992 | Richey, Jr. et al. | 524/507.
|
| 5115025 | May., 1992 | Koleske et al. | 525/162.
|
| 5134205 | Jul., 1992 | Blank | 525/509.
|
| 5300328 | Apr., 1994 | Rehfuss | 427/388.
|
| Foreign Patent Documents |
| 36 34 780 | Apr., 1987 | DE.
| |
| 37 26 956A1 | Feb., 1989 | DE.
| |
| 38 11 497A1 | Oct., 1989 | DE.
| |
| 39 29 697A1 | Mar., 1991 | DE.
| |
| 38 33 890A1 | Apr., 1991 | DE.
| |
| 0 257848 | Mar., 1988 | EP.
| |
| 0 365098 | Apr., 1990 | EP.
| |
| 0 594142 | Apr., 1994 | EP.
| |
| 929973 | Jun., 1963 | GB.
| |
| 51-4124 | Jan., 1976 | JP.
| |
| WO87/00851 | Feb., 1987 | WO.
| |
Other References
Balwant Singh et al., Xvth International Conference in Organic Coatings
Science and Technology, Athens, Greece 15, 385 (Jul., 1989).
|
Primary Examiner: Wu; David W.
Assistant Examiner: Zalukaeva; Tanya
Attorney, Agent or Firm: Uhl; William J., Altman; Deborah M.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation in-part of application Ser. No.
08/968,105, filed Nov. 12, 1997, which is a continuation of application
Ser. No. 08/329,915, filed Oct. 27, 1994, now abandoned, which is a
continuation of application Ser. No. 07/968,786, filed Oct. 30, 1992, now
abandoned.
Claims
We claim:
1. A copolymer composition comprising (meth)acrylate copolymers based on
the copolymerization product of (a) hydroxyl functional (meth)acrylate
monomers and (b) (meth)acrylate esters of hydroxyalkyl carbamates, with
other (meth)acrylate comonomers.
2. The copolymer composition of claim 1 wherein the hydroxyl functional
(meth)acrylate monomer is a hydroxyl functional (meth)acrylate monomer
selected from the group consisting of hydroxy ethyl (meth)acrylate and
hydroxy propyl (meth)acrylate.
3. The copolymer composition of claim 1 wherein the (meth)acrylate esters
of hydroxyalkyl carbamates has the formula:
##STR3##
wherein R is hydrogen or methyl; R' is hydrogen; R" is hydrogen or alkyl of
1-18 carbon atoms; and X is alkyl.
4. The copolymer composition of claim 3 wherein R" is hydrogen and the
hydroxyalkyl carbamate (meth)acrylate is selected from the group
consisting of hydroxy ethyl carbamate (meth)acrylate, and hydroxy propyl
carbamate (meth)acrylate.
5. The copolymer composition of claim 1 wherein said other (meth)acrylate
comonomers are selected from the group consisting of alkyl esters of
acrylic acid and methacrylic acid.
6. The copolymer composition of claim 1 further comprising ethylenically
unsaturated monomers copolymerized with said component (a) and component
(b) and other (meth)acrylate comonomers.
Description
FIELD OF THE INVENTION
The present invention relates to aminoplast curable film-forming
compositions, and in particular to aminoplast curable compositions
exhibiting superior acid etch resistance.
BACKGROUND OF THE INVENTION
Aminoplast-cured coating systems are well known and provide many excellent
coating properties. However, it is widely recognized that such coatings,
particularly clear coats, have poor resistance to etching by acid.
Conventional coating systems that contain hydroxyl functional film-forming
resins and aminoplast crosslinking agents rely on a cure mechanism wherein
hydroxyl groups on the resin react with the aminoplast to form ether
linkages. See, for example, European Patent Application 0 257 848.
Although not intending to be bound by any theory, it is believed that such
ether linkages are vulnerable to acid attack and hence yield coatings with
poor acid etch resistance.
Because many geographic areas encounter acidic precipitation, acid
resistance in coatings is becoming an increasingly desirable property,
particularly for automotive coatings. Hydroxyl-aminoplast coating systems
of the prior art are not highly effective for providing protection against
etching caused by acid rain.
It is desirable, therefore, to provide a coating system which avoids the
problems of the prior art by demonstrating improved acid etch resistance
properties.
SUMMARY OF THE INVENTION
In accordance with the present invention, a curable film-forming
composition is provided, derived from (1) a material containing a
plurality of terminal or pendant groups of the structure:
##STR1##
where X is --N or --O and R is H or alkyl of 1 to 18 carbon atoms or R is
bonded to X and forms part of a 5 or 6 membered ring and R' is alkyl of 1
to 18 carbon atoms; and (2) an aminoplast crosslinking agent containing
methylol and/or methylol ether groups. Prior to crosslinking, the
film-forming composition comprising the material of (1) and (2) has a
calculated hydroxyl value less than 50 based on solid weight of the clear
film-forming composition, excluding any hydroxyl functionality which may
be associated with N-methylol groups. The crosslinked coating has a
substantial number of urethane and/or urea crosslinks that arise from
reaction of the terminal or pendant groups of structure I or II with the
aminoplast, thereby providing a high level of acid etch resistance.
DETAILED DESCRIPTION
The film-forming composition is a crosslinkable composition comprising (1)
a material containing a plurality of pendant or terminal groups of the
structure:
##STR2##
where X is --N or --O and R is H or alkyl of 1 to 18, preferably 1 to 6
carbon atoms or R is bonded to X and forms part of a five- or six-membered
ring and R' is alkyl of 1 to 18, preferably 1 to 6 carbon atoms; and (2)
an aminoplast crosslinking agent containing methylol and/or methylol ether
groups. The material of (1) has on average at least two pendant or
terminal groups of the structure I and/or II, preferably structure I, per
molecule. Preferably X=--O. The material of (1) may be an acrylic polymer,
a polyester polymer or oligomer, a polyurethane polymer or oligomer, or a
blend of two or more of these materials. Acrylic polymers are preferred.
Prior to crosslinking, the film-forming composition of (1) and (2) has a
theoretical hydroxyl value of less than 50, preferably less than 25, and
more preferably 0, based on solid weight of the film-forming composition,
excluding any hydroxyl functionality associated with N-methylol groups
such as those in the aminoplast and any hydroxyl functionality which may
be associated with N-methylol groups incorporated into the material of (1)
such as N-methylol acrylamide groups in the acrylic polymer. By calculated
hydroxyl value is meant the calculated value based on the relative amounts
of the various ingredients used in making the film-forming composition,
rather than the actual hydroxyl value which is measured on the
film-forming composition itself by conventional techniques. The resultant
crosslinked coating contains a substantial number of urethane or urea
crosslinks that arise from reaction of the terminal or pendant groups of
structure I or II with the aminoplast, thereby providing a high level of
acid etch resistance.
The acrylic materials are copolymers of one or more alkyl esters of acrylic
acid or methacrylic acid, and, optionally, one or more other polymerizable
ethylenically unsaturated monomers. Suitable alkyl esters of acrylic or
methacrylic acid include methyl methacrylate, ethyl methacrylate, butyl
methacrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate.
Suitable other polymerizable ethylenically unsaturated monomers include
vinyl aromatic compounds such as styrene and vinyl toluene; nitriles such
as acrylonitrile and methacrylonitrile; vinyl and vinylidene halides such
as vinyl chloride and vinylidene fluoride and vinyl esters such as vinyl
acetate; and acid functional monomers such as acrylic and methacrylic
acid.
Hydroxyl functional monomers such as hydroxyethyl acrylate, hydroxypropyl
acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate may be
copolymerized with the acrylic monomers to impart hydroxyl functionality
to the acrylic material in accordance with the theoretical hydroxyl values
mentioned above.
Pendant carbamate functional groups of structure I (X=-O) may be
incorporated into the acrylic polymer by copolymerizing the acrylic
monomers with a carbamate functional vinyl monomer, for example a
carbamate functional alkyl ester of methacrylic acid. These carbamate
functional alkyl esters are prepared by reacting, for example, a
hydroxyalkyl carbamate, such as the reaction product of ammonia and
ethylene carbonate or propylene carbonate, with methacrylic anhydride.
Other carbamate functional vinyl monomers are, for instance, the reaction
product of hydroxyethyl methacrylate, isophorone diisocyanate, and
hydroxypropyl carbamate (yielding structure I), or the reaction product of
hydroxypropyl methacrylate, isophorone diisocyanate, and methanol
(yielding structure II). Still other carbamate functional vinyl monomers
may be used, such as the reaction product of isocyanic acid (HNCO) with a
hydroxyl functional acrylic or methacrylic monomer such as hydroxyethyl
acrylate, and those described in U.S. Pat. No. 3,479,328. Pendant
carbamate groups can also be incorporated into the acrylic polymer by
reacting a hydroxyl functional acrylic polymer with a low molecular weight
alkyl carbamate such as methyl carbamate. Reference is made to Japanese
Kokai 51-4124. Also, hydroxyl functional acrylic polymers can be reacted
with isocyanic acid yielding pendant carbamate groups. Note that the
production of isocyanic acid is disclosed in U.S. Pat. No. 4,364,913.
Likewise, hydroxyl functional acrylic polymers can be reacted with urea to
give an acrylic polymer with pendant carbamate groups.
Pendant urea groups of structure I (X=-N) may be incorporated into the
acrylic polymer by copolymerizing the acrylic monomers with urea
functional vinyl monomers such as urea functional alkyl esters of acrylic
acid or methacrylic acid. Examples include the condensation product of
acrylic acid or methacrylic acid with a hydroxyalkyl ethylene urea such as
hydroxyethyl ethylene urea. Other urea functional monomers are, for
example, the reaction product of hydroxyethyl methacrylate, isophorone
diisocyanate, and hydroxyethyl ethylene urea.
Mixed pendant carbamate and urea groups may also be used.
The acrylic polymer material may be prepared by solution polymerization
techniques in the presence of suitable catalysts such as organic peroxides
or azo compounds, for example, benzoyl peroxide or
N,N-azobis(isobutyronitrile). The polymerization may be carried out in an
organic solution in which the monomers are soluble by techniques
conventional in the art. Alternately, the acrylic polymer may be prepared
by aqueous emulsion or dispersion polymerization techniques well known in
the art.
The acrylic material typically has a number average molecular weight of
from about 900 to 13,000, preferably from about 1000 to 5000 as determined
by gel permeation chromatography using a polystyrene standard, and an
equivalent weight of less than 5000, preferably within the range of 140 to
2500, based on equivalents of reactive pendant or terminal carbamate or
carbamate and/or urea groups. The equivalent weight is a calculated value
based on the relative amounts of the various ingredients used in making
the acrylic material and is based on solids of the acrylic material.
Polyesters may also be used in the formulation of the film-forming
composition and may be prepared by the polyesterification of a
polycarboxylic acid or anhydride thereof with polyols and/or an epoxide.
Usually, the polycarboxylic acids and polyols are aliphatic or aromatic
dibasic acids and diols.
The polyols which are usually employed in making the polyester include
alkylene glycols, such as ethylene glycol, 1,6-hexanediol, neopentyl
glycol, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate and
other glycols, such as hydrogenated Bisphenol A, cyclohexanediol,
cyclohexanedimethanol, caprolactone-based diols, for example, the reaction
product of epsilon-caprolactone and ethylene glycol, hydroxy-alkylated
bisphenols, polyether glycols, for example, poly(oxytetramethylene) glycol
and the like. Polyols of higher functionality may also be used. Examples
include trimethylolpropane, trimethylolethane, pentaerythritol and the
like.
The acid component of the polyester consists primarily of monomeric
carboxylic acids or anhydrides thereof having 2 to 18 carbon atoms per
molecule. Among the acids which are useful are phthalic acid, isophthalic
acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid,
methyl hexahydrophthalic anhydride, adipic acid, azelaic acid, sebacic
acid, maleic acid, glutaric acid, decanoic diacid, dodecanoic diacid and
other dicarboxylic acids of various types. The polyester may include minor
amounts of monobasic acids such as benzoic acid, stearic acid, acetic
acid, and oleic acid. Also, there may be employed higher carboxylic acids
such as trimellitic acid and tricarballylic acid. Where acids are referred
to above, it is understood that anhydrides thereof which exist may be used
in place of the acid. Also, lower alkyl esters of the acids such as
dimethyl glutarate and dimethyl terephthalate may be used.
Pendant carbamate functional groups of structure I may be incorporated into
the polyester by first forming a hydroxyalkyl carbamate which can be
reacted with the polyacids and polyols used in forming the polyester. A
polyester oligomer may be prepared by reacting a polycarboxylic acid such
as those mentioned above with a hydroxyalkyl carbamate. An example of a
hydroxyalkyl carbamate is the reaction product of ammonia and ethylene
carbonate or propylene carbonate. The hydroxyalkyl carbamate is condensed
with acid functionality on the polyester or polycarboxylic acid, yielding
pendant carbamate functionality. Pendant carbamate functional groups of
structure I may also be incorporated into the polyester by reacting
isocyanic acid or a low molecular weight alkyl carbamate such as methyl
carbamate with a hydroxyl functional polyester. Also, pendant carbamate
functionality may be incorporated into the polyester by reacting a hydroxy
functional polyester with urea.
Pendant urea groups of structure I may be incorporated into the polyester
by reacting a hydroxyl functional urea such as a hydroxyalkyl ethylene
urea with the polyacids and polyols used in making the polyester. A
polyester oligomer can be prepared by reacting a polyacid with a hydroxyl
functional urea. Also, isocyanate terminated polyurethane or polyester
prepolymers may be reacted with primary amines, aminoalkyl ethylene urea,
or hydroxyalkyl ethylene urea to yield materials with pendant urea groups.
Preparation of these polymers is known in the art and is described in U.S.
Pat. No. 3,563,957.
Mixed pendant carbamate and urea groups may also be used in the polyester
material.
Polyurethanes can be formed by reacting a polyisocyanate with a polyester
having hydroxyl functionality and containing the pendant carbamate and/or
urea groups. Alternatively, the polyurethane can be prepared by reacting a
polyisocyanate with a polyester polyol and a hydroxyalkyl carbamate or
isocyanic acid as separate reactants. Examples of suitable polyisocyanates
are aromatic and aliphatic polyisocyanates, with aliphatic being preferred
because of better color and durability properties. Examples of suitable
aromatic diisocyanates are 4,4'-diphenylmethane diisocyanate,
1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, and toluene
diisocyanate. Examples of suitable aliphatic diisocyanates are straight
chain aliphatic diisocyanates such as 1,4-tetramethylene diisocyanate and
1,6-hexamethylene diisocyanate. Also, cycloaliphatic diisocyanates can be
employed and are preferred because of imparting hardness to the product.
Examples include 1,4-cyclohexyl diisocyanate, isophorone diisocyanate,
alpha, alpha-xylylene diisocyanate and 4,4'-methylene-bis-(cyclohexyl
isocyanate).
The polyester or polyurethane materials typically have number average
molecular weights of about 300 to 3000, preferably about 300 to 600 in
solvent borne systems and about 900 to 1500 in water borne systems as
determined by gel permeation chromatography using a polystyrene standard,
and an equivalent weight of from about 140 to 2500 based on equivalents of
pendant carbamate and/or urea groups. The equivalent weight is a
calculated value based on the relative amounts of the various ingredients
used in making the polyester or polyurethane and is based on solids of the
material.
Besides polymeric materials, relatively low molecular weight materials
containing pendant carbamate functional groups of structure II may be
formed by reacting isocyanate terminated monomers or oligomers, such as an
isocyanurate of polymeric 1,6-hexamethylene diisocyanate, with an alcohol.
Any suitable aliphatic, cycloaliphatic, aromatic alkyl monoalcohol or
phenolic compound may be used, such as, for example, aliphatic alcohols
containing from 1 to 18, preferably lower aliphatic alcohols containing
from 1 to 6 carbon atoms such as methanol, ethanol, n-butyl alcohol and
n-hexanol; cycloaliphatic alcohols such as cyclohexanol; aromatic-alkyl
alcohols such as phenyl carbinol and methylphenyl carbinol; phenolic
compounds such as phenol itself, and substituted phenols in which the
substituents do not adversely affect coating operations. Examples include
cresol and nitrophenol.
It is possible to prepare blends of the acrylic, polyester, and
polyurethane materials containing pendant or terminal carbamate and/or
urea groups described above. It is also possible to prepare blends of the
low molecular weight materials containing pendant carbamate and/or urea
groups with the polymeric materials containing pendant carbamate and/or
urea groups. The weight ratio of low molecular weight materials to
polymeric materials may range from 10:90 to 90:10, preferably 10:90 to
40:60.
The film-forming composition also includes an aminoplast crosslinking agent
containing methylol and/or methylol ether groups. Aminoplast condensates
are obtained from the reaction of formaldehyde with an amine or amide. The
most common amines or amides are melamine, urea, or benzoguanamine, and
are preferred. However, condensates with other amines or amides can be
used; for example, aldehyde condensates of glycoluril, which give a high
melting crystalline product which is useful in powder coatings. While the
aldehyde used is most often formaldehyde, other aldehydes such as
acetaldehyde, crotonaldehyde, and benzaldehyde may be used.
The aminoplast contains methylol groups and preferably at least a portion
of these groups are etherified with an alcohol to modify the cure
response. Any monohydric alcohol may be employed for this purpose
including methanol, ethanol, butanol, and hexanol.
Preferably, the aminoplasts which are used are melamine-, urea-, or
benzoguanamine-formaldehyde condensates etherified with an alcohol
containing from 1 to 6 carbon atoms. The aminoplast is present in amounts
of about 1 to 80, preferably 10 to 50 percent by weight based on weight of
resin solids in the clear film-forming composition. The equivalent ratio
of pendant or terminal carbamate and/or urea functional groups of
structure I and II above to methylol or methylol ether groups is 0.5 to
2:1 based on calculated equivalent weights, and being sufficient to form a
crosslinked film.
The film-forming composition may be solvent borne, in which the carbamate
and/or urea functional materials are dissolved in one or more nonreactive
organic solvents. Suitable components of the solvent system which may be
used are alcohols such as n-propanol and n-butanol, ethers such as
ethylene glycol dibutyl ether and diethylene glycol dibutyl ether, ketones
such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone
and methyl N-butyl ketone; esters such as butyl acetate, 2-ethoxyethyl
acetate and hexyl acetate; aliphatic and alicyclic hydrocarbons such as
the various petroleum naphthas and cyclohexane; and aromatic hydrocarbons
such as toluene and xylene. The amount of solvent used generally can range
from about 0 to 55 percent, preferably from about 0 to 50 percent, and
most preferably from about 40 to 50 percent by weight based on the total
weight of the coating composition.
The film-forming composition may also be waterborne. For example,
acid-functional materials having terminal or pendant carbamate and/or urea
groups may be neutralized with amines and dissolved or dispersed in water.
Also, it is possible to prepare an aqueous dispersion of a blend of
acrylic and polyester and/or polyurethane materials with pendant carbamate
and/or urea groups in microparticulate form by a high stress technique
using a homogenizer. This technique is described in U.S. Pat. No.
5,071,904.
Powder coatings, i.e., film-forming composition is a solid, may also be
prepared from the carbamate and/or urea functional materials of the
present invention. Monomers used to form the carbamate and/or urea
functional materials are selected such that the resultant material has a
high glass transition temperature (Tg); that is, greater than 60.degree.
C. This material can then be combined with an aldehyde condensate of
glycoluril as mentioned above to form the resinous binder portion of the
powder coating composition. Preferably, the film-forming composition is a
liquid.
The film-forming composition will also preferably contain catalysts to
accelerate the cure of the aminoplast and carbamate or urea groups.
Examples of suitable catalysts are acidic materials and include sulfonic
acids or substituted sulfonic acids such as para-toluenesulfonic acid. The
catalyst is usually present in an amount of about 0.5 to 5.0 percent by
weight, preferably about 1 to 2 percent by weight, based on weight of
total resin solids. Optional ingredients such as, for example,
plasticizers, flow controllers, anti-oxidants, UV light absorbers and
similar additives conventional in the art may be included in the
composition. These ingredients are typically present at up to 25% by
weight based on total resin solids.
The composition may be applied to a substrate, or in the case of a clear
film-forming composition, to a basecoated substrate by any conventional
coating technique such as brushing, spraying, dipping or flowing, but
spray applications are preferred because of superior gloss. Any of the
known spraying techniques may be employed such as compressed air spraying,
electrostatic spraying and either manual or automatic methods.
After application of the coating composition, the coated substrate is
heated to cure the coating. In the curing operation, solvents are driven
off and the film-forming material of the coating is crosslinked. The
heating or curing operation is usually carried out at a temperature in the
range of from 160-350.degree. F. (71-177.degree. C.) but if needed, lower
or higher temperatures may be used as necessary to activate crosslinking
mechanisms. The thickness of the coating is usually from about 0.5-5,
preferably 1.2-3 mils.
The invention will further be described by reference to the following
examples. Unless otherwise indicated, all parts are by weight.
EXAMPLES
The following examples (Examples A-N) show the preparation of carbamate
and/or urea functional materials and corresponding hydroxyl functional
materials.
Example A
A carbamate functional acrylic monomer was prepared from the following
ingredients:
Ingredient Weight in Grams
isophorone diisocyanate (IPDI) 888.0
dibutyl tin dilaurate 4.6
2,6-di-t-butyl methyl phenol 2.6
butyl methacrylate 282.0
hydroxypropyl carbamate 571.2
hydroxyethyl methacrylate 416.0
A suitable reactor was charged with the first four ingredients and heated
to a temperature of 60.degree. C. The hydroxypropyl carbamate was added to
the reaction mixture over 2 hours. The reaction mixture was then held at
60.degree. C. until the isocyanate equivalent weight became constant. The
hydroxyethyl methacrylate was then added over 2 hours, and the reaction
held until infrared analysis indicated the absence of isocyanate. The
product was diluted with 346.0 g of butyl methacrylate. The final product
had a solids content of 75% and had a number average molecular weight of
622 as determined by gel permeation chromatography.
Example B
A low molecular weight, carbamate functional material was prepared from the
following ingredients:
Ingredient Weight in Grams
DESMODUR N-3300.sup.1 3300.0
dibutyl tin dilaurate 4.0
butyl acetate 1592.0
methanol 613.7
.sup.1 Isocyanurate of hexamethylene diisocyanate, available from Miles,
Inc.
A suitable reactor was charged with the first three ingredients and heated
to a temperature of 60.degree. C. The methanol was added to the reaction
mixture over 2 hours. The temperature rose to 74.degree. C. and then was
held at 80.degree. C. until infrared analysis indicated the absence of
isocyanate (one and a half hours). The final product had a Gardner-Hold
viscosity of N--O and a number average molecular weight of 961 as
determined by gel permeation chromatography.
Example C
A hydroxyl functional acrylic polymer was prepared from the following
ingredients:
Ingredient Weight in Grams
hydroxyethyl acrylate 200.0
butyl methacrylate 584.0
.alpha.-methyl styrene dimer 16.0
LUPERSOL 555M60.sup.1 80.0
t-butyl perbenzoate 24.0
.sup.1 t-amyl peracetate available from Atochem.
A blend of EKTAPRO EEP (ethyl 3-ethoxypropionate available from Eastman
Chemicals, 236.8 g) and butyl acetate (105.2 g) was charged to a suitable
reactor and heated to reflux. The first three ingredients were mixed with
50 g EKTAPRO EEP. The t-amyl peracetate and 80 g EKTAPRO EEP were also
mixed together. The premixture of acrylic monomers and the premixture of
initiator were added simultaneously to the reaction vessel over a period
of about 3 hours while maintaining the reaction at reflux. At the
completion of the addition, the reaction mixture was held at reflux for
one hour followed by the addition of 8.0 g t-butyl perbenzoate over about
30 minutes. The reaction was then held for 30 minutes at reflux. 8.0 more
grams of t-butyl perbenzoate was added over 30 minutes and the reaction
held for 30 minutes at reflux. The remainder of t-butyl perbenzoate was
added over 30 minutes and the reaction held at reflux for two hours. An
additional total of about 54 grams of EKTAPRO EEP was added to the
reaction mixture to adjust the solids content to about 60%. The reaction
mixture was then cooled to room temperature. The final product had a
solids content of 57% and had a number average molecular weight of 1220 as
determined by gel permeation chromatography. The acrylic polymer had a
hydroxyl number of about 92.2 based on solids.
Example D
A carbamate functional acrylic polymer was prepared from the following
ingredients:
Ingredient Weight in Grams
butyl acetate 332.0
EKTAPRO EEP 103.0
carbamate functional acrylic monomer 349.9
from Example A
butyl methacrylate 279.1
.alpha.-methyl styrene dimer 12.5
t-amyl peracetate 63.2
butyl acetate 81.4
A suitable reactor was charged with the first two ingredients and heated to
reflux. The carbamate functional acrylic monomer, butyl methacrylate and
.alpha.-methyl styrene dimer were added to the reaction mixture over 3
hours. The t-amyl peracetate and butyl acetate were then added over 3.5
hours. The reaction was then held at reflux for one hour, and cooled to
room temperature. The final product had a solids content of 49.9% and had
a number average molecular weight of 1346 as determined by gel permeation
chromatography. The carbamate equivalent weight of the resultant material
was approximately 900.
Example E
A carbamate functional acrylic polymer dispersed in aqueous medium was
prepared from the following ingredients:
Ingredient Weight in Grams
n-propanol 350.0
butyl acrylate 202.0
methyl methacrylate 195.2
carbamate functional acrylic monomer 349.9
from example A
acrylic acid 25.0
t-dodecyl mercaptan 3.2
t-butyl peroctoate 14.4
n-propanol 46.4
dimethyl ethanol amine (DMEA) 23.2
water 700.0
A suitable reactor was charged with the n-propanol and heated to reflux.
The next five ingredients were added to the reaction mixture over 3 hours.
At the same time, the t-butyl peroctoate and 46.4 g n-propanol were added
over 3.5 hours. The reaction was then held at reflux for one hour. The
DMEA was added to the reaction mixture at about 95.degree. C., followed by
addition of the water. The reaction cooled to room temperature. The final
product had a solids content of 35.3% and had a number average molecular
weight of 3728 as determined by gel permeation chromatography. The
carbamate equivalent weight of the resultant material was approximately
1040.
Example F
A carbamate functional acrylic latex was prepared from the following
ingredients:
Ingredient Weight in Grams
Feed A: water 783.4
ALIPAL CO-436.sup.1 15.1
sodium bicarbonate 1.8
Feed B: water 114.8
ammonium persulfate 5.2
Feed C: butyl acrylate 277.5
methyl methacrylate 263.7
carbamate functional acrylic 502.0
monomer from Example A
butyl methacrylate 136.9
acrylic acid 36.4
t-dodecyl mercaptan 18.2
water 757.7
ALIPAL CO-436 17.4
DDBSA-DMEA.sup.2 11.5
Feed D: diisopropanol amine, 50% in water 67.2
.sup.1 Anionic ethoxylated nonyl phenol available from GAF Corporation.
.sup.2 DDBSA-DMEA solution was prepared by dissolving 1 mole dodecyl
benzene sulfonic acid in water containing 1 mole dimethy1 ethanolamine.
A suitable reactor was charged with Feed A and heated to 80.degree. C. 25 g
of Feed C and then all of Feed B were added to the reaction mixture, and
the mixture was held for 20 minutes. The remainder of Feed C was added
over 3 hours. The reaction was held at 80.degree. C. for two hours, and
then cooled to room temperature. After dilution with Feed D, the final
product had a solids content of 42.8% and had a number average molecular
weight of 12,393 as determined by gel permeation chromatography. The
carbamate equivalent weight of the resultant material was approximately
1140.
Example G
A urea functional polyester oligomer was prepared from the following
ingredients:
Ingredient Weight in Grams
Methylhexahydrophthalic anhydride 840.95
hydroxyethylethylene urea.sup.1 1275.47
butyl stannoic acid 2.12
triphenyl phosphite 4.23
xylene 226.1
water 101.7
n-propanol 406.9
.sup.1 Available from Union Carbide as UCar RD-65-1.
The first five ingredients were charged to a suitable reactor equipped with
a nitrogen sparge and Dean-Stark trap and heated to reflux. As water was
removed from the reaction (88.2 g), the acid value of the reaction mixture
dropped to less than 5. The reaction mixture was then vacuum stripped to
remove xylene, cooled to 70.degree. C., and diluted with the n-propanol
and water. The reaction mixture had a final measured solids content of
77%, a number average molecular weight of 177 and a weight average
molecular weight of about 247 as determined by gel permeation
chromatography using a polystyrene standard.
Example H
A carbamate functional polyester oligomer was prepared from the following
ingredients:
Ingredient Weight in Grams
Methylhexahydrophthalic anhydride 505.68
ESTERDIOL 204.sup.1 716.04
butyl stannoic acid 2.12
urea 120
xylene 50
n-propanol 1180
.sup.1 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate
available from Union Carbide.
The first three ingredients were charged to a suitable reactor equipped
with a nitrogen sparge and Dean-Stark trap and heated to reflux. As water
was removed from the reaction, the acid value of the reaction mixture
dropped to less than 1. The reaction mixture was then cooled to
150.degree. C., and the urea and xylene were added. The reaction mixture
was held at reflux for 28 hours and then vacuum stripped to remove xylene.
After dilution with the n-propanol, the reaction mixture had a final
measured solids content of 52.6%, and a viscosity of A on the Gardner-Hold
scale.
Example I
A carbamate functional polyester was prepared from the following
ingredients:
Ingredient Weight in Grams
DOWANOL PM carbamate.sup.2 332.5
polyester.sup.1 455
butyl stannoic acid 2.12
.sup.1 Reaction product of hexahydrophthalic anhydride, ESTERDIOL 204, and
1,6-hexanediol in a 1:1:1 mole ratio.
.sup.2 Reaction product of DOWANOL PM and urea, 95% in DOWANOL PM which is
the monomethyl ether of propylene glycol and is available from Dow
Chemical Co.
The ingredients were charged to a suitable reactor equipped with a nitrogen
sparge and Dean-Stark trap and heated to 140-145.degree. C. DOWANOL PM was
removed from the reaction under reduced pressure. The reaction mixture was
held until DOWANOL PM carbamate was no longer detectable on a gas
chromatograph. The resultant reaction mixture was a soft, waxy, opaque
material.
Example J
A pre-emulsion was prepared by stirring together the following ingredients:
Ingredient Weight in Grams
carbamate functional polyester 125.0
of Example I
methyl methacrylate 100.0
butyl acrylate 100.0
stearyl methacrylate 25.0
N-methylol acrylamide
(48% solution in water) 83.4
methacrylic acid 10.0
dodecylbenzenesulfonic acid (70% in water) 14.3
N,N-dimethyl ethanol amine 2.5
IGEPAL Co-897.sup.1 7.2
ferrous ammonium suifate, 1% in water 2.5
water 500.0
.sup.1 Nonionic ethoxylated nonyl phenol available from GAF Corp.
The pre-emulsion was passed though an M110 MICROFLUIDIZER high pressure
impingement emulsifier (available from Microfluidics, Inc.) at 8000 psi to
produce a bluish-white emulsion. The emulsion was transferred to a
suitable reactor and blanketed with nitrogen. Polymerization was initiated
by adding first a mixture of 1.5 g isoascorbic acid and 2.5 g
mercaptopropionic acid dissolved in 50.0 g water followed by a solution of
2.19 g hydrogen peroxide (35%) in 25.0 g water added dropwise over 15
minutes. The emulsion exothermed from 26 to 66.degree. C. over 14 minutes.
Any remaining monomer was then polymerized by adding 0.5 g isoascorbic
acid dissolved in 5.0 g water followed by 0.5 g of 35% hydrogen peroxide.
An additional exotherm from 56 to 59.degree. C. was observed. The pH of
the latex was increased to 7.0 with 16.45 g of a 1:1 mixture of water and
diisopropanolamine. The final product had a solids content of 41.0%.
Example K
A urea functional polyester oligomer was prepared from the following
ingredients:
Ingredient Weight in Grams
dodecanedioic acid 575.0
hydroxyethyl ethylene urea 637.74
butyl stannoic acid 1.21
xylene 198.66
The ingredients were charged to a suitable reactor and heated to reflux to
remove water through a Dean-Stark trap. The temperature of the reaction
mixture was held at reflux until the acid value was less than 5. The
reaction mixture was then cooled to 120.degree. C. and volatile materials
in the reaction mixture were removed under vacuum to a solids content of
98.7%. The reaction mixture was diluted to a final solids content of 65%
with an 80:20 weight mixture of propanol:water. The product had a number
average molecular weight of 606 and a urea equivalent weight of
approximately 230.
Example L
A cazbamate functional acrylic monomer was prepared from the following
ingredients:
Ingredient Weight in Grams
hydroxypropyl carbamate 600.0
2,6-di-t-butyl methyl phenol 3.9
triphenyl phosphite 2.22
methacrylic anhydride 810.0
toluene 1200.0
sodium hydroxide (16.7%) 1260.0
A suitable reactor was charged with the first four ingredients and heated
to 100.degree. C. The reaction mixture was held at this temperature until
the methacrylic anhydride had completely reacted with the hydroxypropyl
carbamate, as determined by gas chromatography. The reaction was cooled to
room temperature and the toluene and sodium hydroxide were added. After
agitating for about 30 minutes, the reaction mixture was transferred to a
separatory funnel. The top layer, containing the product in toluene, was
collected in a flask and the toluene was removed by vacuum distillation.
Example M
A carbamate functional acrylic latex was prepared from the following
ingredients:
Ingredient Weight in Grams
Feed A: water 450.0
ALIPAL CO-436 9.3
sodium bicarbonate 0.8
Feed B: water 50.0
ammonium persulfate 2.2
Feed C: carbamate functional acrylic 180.0
monomer of Example L
butyl acrylate 240.0
methyl methacrylate 120.0
styrene 60.0
acrylic acid 16.8
t-dodecyl mercaptan 9.0
water 400.0
ALIPAL CO-436 18.0
PGNP-15.sup.1 26.0
Feed D: diisopropanol amine, 50% in water 20.0
.sup.1 Nonionic surfactant prepared by reacting 1 mole of nonyl phenol with
15 moles of glycidol.
A suitable reactor was charged with Feed A and heated to 80.degree. C. 25 g
of Feed C and then all of Feed B were added to the reaction mixture, and
the mixture was held for 20 minutes. The remainder of Feed C was added
over 3 hours. The reaction was held at 80.degree. C. for two hours, and
then cooled to room temperature. After addition of Feed D, the pH was 7.7.
The final product had a solids content of 40.5% and had a number average
molecular weight of 5706 as determined by gel permeation chromatography.
Example N
A hydroxyl functional acrylic latex was prepared from the following
ingredients:
Ingredient Weight in Grams
Feed A: water 450.0
ALIPAL CO-436 9.3
sodium bicarbonate 0.8
Feed B: water 50.0
ammonium persulfate 2.2
Feed C: hydroxyethyl acrylate 180.0
butyl acrylate 240.0
methyl methacrylate 120.0
styrene 60.0
acrylic acid 16.8
t-dodecyl mercaptan 9.0
water 400.0
ALIPAL CO-436 18.0
PGNP-15 26.0
Feed D: diisopropanol amine, 50% in water 20.0
A suitable reactor was charged with Feed A and heated to 80.degree. C. 25 g
of Feed C and then all of Feed B were added to the reaction mixture, and
the mixture was held for 20 minutes. The remainder of Feed C was added
over 3 hours. The reaction was held at 80.degree. C. for two hours, and
then cooled to room temperature. After addition of Feed D, the pH was
7.84. The final product had a solids content of 40.2% and had a number
average molecular weight of 5123 as determined by gel permeation
chromatography, and a hydroxyl value of 22 based on solids content.
The following examples (1-12) show the preparation of various clear
film-forming compositions prepared with carbamate, urea, or hydroxyl
functional materials and aminoplast curing agents. The coating
compositions were evaluated in color-plus-clear applications.
Example 1
A clear film-forming composition was prepared by mixing together the
following ingredients:
Ingredient Solid weight in grams Solution weight in grams
n-butyl acetate -- 7.0
EKTAPRO EEP -- 19.0
TINUVIN 1130.sup.1 3.0 3.0
TINUVIN 292.sup.2 0.3 0.3
polybutylacrylate.sup.3 0.4 0.7
flow control agent.sup.4 1.0 2.3
CYMEL 327.sup.5 30.0 33.3
carbamate containing 69.0 138.8
acrylic of Example D
phenyl acid phosphate 1.0 1.2
.sup.1 Substituted benzotriazole UV light stabilizer available from Ciba
Geigy Corporation.
.sup.2 Sterically hindered tertiary amine light stabilizer available from
Ciba Geigy Corporation.
.sup.3 A flow control agent having a Mw of about 6700 and Mn of about 2600
made in xylene at 62.5% solids.
.sup.4 Polymeric microparticle prepared in accordance with example 11 of
U.S. Pat. No. 4,147,688.
.sup.5 Highly methylated, high imino content aminoplast resin available
from American Cyanamid.
Example 2
A clear film-forming composition was prepared by mixing together the
following ingredients:
Ingredient Solid weight in grams Solution weight in grams
hexyl acetate -- 7.0
EKTAPRO EEP -- 15.1
TINUVIN 1130 3.0 3.0
TINUVIN 292 0.3 0.3
polybutylacrylate 0.4 0.7
flow control agent 1.0 2.3
CYMEL 327 30.0 33.3
carbamate containing 49.0 97.0
acrylic of Example D
hydroxyl containing 20.0 35.1
acrylic of Example C
phenyl acid phosphate 1.0 1.2
Example 3
A clear film-forming composition was prepared by mixing together the
following ingredients:
Ingredient Solid weight in grams Solution weight in grams
hexyl acetate -- 7.0
EKTAPRO EEP -- 18.8
TINUVIN 1130 3.0 3.0
TINUVIN 292 0.3 0.3
polybutylacrylate 0.4 0.7
flow control agent 1.0 2.3
CYMEL 327 30.0 33.3
carbamate containing 29.0 57.3
acrylic of Example D
hydroxyl containing 40.0 70.1
acrylic of Example C
phenyl acid phosphate 1.0 1.2
Example 4
A clear film-forming composition was prepared by mixing together the
following ingredients:
Ingredient Solid weight in grams Solution weight in grams
hexyl acetate -- 7.0
EKTAPRO EEP -- 19.3
TINUVIN 1130 3.0 3.0
TINUVIN 292 0.3 0.3
polybutylacrylate 0.4 0.7
flow control agent 1.0 2.3
CYMEL 327 30.0 33.3
carbamate containing 9.0 17.8
acrylic of Example D
hydroxyl containing 60.0 105.1
acrylic of Example C
phenyl acid phosphate 1.0 1.2
Example 5
A clear film-forming composition was prepared by mixing together the
following ingredients:
Ingredient Solid weight in grams Solution weight in grams
n-butyl acetate -- 7.0
EKTAPRO EEP -- 15.0
TINUVIN 1130 3.0 3.0
TINUVIN 292 0.3 0.3
polybutylacrylate 0.4 0.7
flow control agent 1.0 2.3
CYMEL 327 30.0 33.3
hydroxyl containing 69.0 120.7
acrylic of Example C
phenyl acid phosphate 1.0 1.2
Example 6
A clear film-forming composition was prepared by mixing together the
following ingredients:
Solid
Ingredient weight in grams Solution weight in grams
n-amyl alcohol -- 35.1
TINUVIN 1130 3.0 3.0
TINUVIN 292 0.3 0.3
polybutylacrylate 0.4 0.7
low molecular weight 11.1 15.9
carbamate functional
material of Example B
carbamate functional 32.5 64.2
acrylic of Example D
urea functional 11.1 14.4
polyester of Example G
carbamate functional 10.3 17.3
polyester of Example H
phenyl acid phosphate 1.0 1.2
The film-forming compositions of Examples 1-6 were applied to a pigmented
basecoat to form color-plus-clear composite coatings over electrocoated
steel substrates. The pigmented basecoat for Examples 1-6 is commercially
available from PPG Industries, Inc. and identified as NHU-9517. The
basecoat was pigmented black in color. The electrocoat used on the steel
is commercially available from PPG Industries, Inc. and is identified as
ED-11.
The basecoat was spray applied in two coats to electrocoated steel panels
at a temperature of about 75.degree. F. (24.degree. C.). A ninety second
flash time was allowed between the two basecoat applications. After the
second basecoat application, a flash time of approximately five minutes
was allowed at 75.degree. F. (24.degree. C.) before the application of the
clear coating composition. The clear coating compositions of Examples 1-6
were each applied to a basecoated panel in two coats with a ninety second
flash at 75.degree. F. (24.degree. C.) allowed between coats. The
composite coating was allowed to air flash at 75.degree. F. (24.degree.
C.) for ten to fifteen minutes before baking at 285.degree. F.
(141.degree. C.) for 30 minutes to cure both the basecoat and clearcoat.
The panels were baked in a horizontal position. The properties of the
composite coatings are reported in Table I below.
TABLE I
Hydroxyl
Number of Pencil Hardness
Comp- % OH Functional Acid Etch After 3 Minute
Example osition Resin by Weight Rating* Xylene Spot**
1 0 0 3 F
2 23 20 4 F
3 46 40 5 F
4 69 60 8 F
5 115 100 8 H
6 0 0 3 H
*Panels were sprayed with a sulfurous acid solution (350 grams deionized
water and 12 grams sulfurous acid to give a pH of 2.0 plus or minus 0.1)
using a polyethylene spray bottle, giving a distribution of drop sizes up
to one quarter inch. Approximately 2.5 to 3.0 grams of solution were
applied per 4 .times. 4 inch panel. The panels were then placed in an oven
at 110.degree. F. (43.degree. C.) for twenty minutes. The panels were
removed from the oven and the spray/bake procedure
# was repeated two more times to give a total of 60 minutes at 110.degree.
F. (43.degree. C.). After the third cycle the panels were washed with soap
and water and dried, then rated for degree of acid etch resistance on a
scale of 1-10 (1 = no observable etching; 10 = severe etching).
**Pencil hardness (Gouge hardness) determined by ASTM D 3353-74 was
performed immediately after the panel was spotted with a 0.5 inch to 2
inch drop of xylene and wiped dry.
Example 7
A clear film-forming composition was prepared by mixing together the
following ingredients:
Ingredient Solid weight in grams Solution weight in grams
TINUVIN 1130 3.5 3.5
CYMEL 328.sup.1 30.0 34.9
carbamate containing 70.0 198.4
acrylic of Example E
phenyl acid phosphate 1.0 5.0
water -- 137.0
.sup.1 Waterborne version of CYMEL 327 available from American Cyanamid.
Example 8
A clear film-forming composition was prepared by mixing together the
following ingredients:
Solid weight Solution weight
Ingredient in grams in grams
carbamate containing 70.0 162.6
acrylic of Example F
CYMEL 303.sup.1 30.0 30.0
TINUVIN 1130 3.5 3.5
DDBSA solution.sup.2 1.0 5.0
FC 430 solution.sup.3 0.1 2.0
diisopropanol amine solution.sup.4 -- 3.9
n-methyl-2-pyrrolidone -- 5.0
isopropanol -- 5.0
water -- 25.0
.sup.1 Hexamethoxymethyl melamine resin available from American Cyanamid.
.sup.2 20 weight percent solution of dodecylbenzene sulfonic acid
neutralized with diisopropanolamine in deionized water.
.sup.3 Nonionic surfactant available from 3M Corporation.
.sup.4 50 weight percent solution of diisopropanolamine in deionized water.
Example 9
A clear film-forming composition was prepared by mixing together the
following ingredients:
Solid weight
Ingredient in grams Solution weight in grams
DDDA/HEEU oligomer 70.0 116.7
of Example K
CYMEL 328 30.0 34.9
Phenyl acid 1.0 5.0
phosphate solution
Tego Wet ZFS 453.sup.1 0.09 0.36
.sup.1 Nonionic surfactant available from Tego Chemie Service GmbH.
Example 10
A clear film-forming composition was prepared by mixing together the
following ingredients:
Solid weight
Ingredient in grams Solution weight in grams
carbamate functional 70.0 170.61
acrylic and polyester
latex of Example J
CYMEL 303 30.0 30.0
TINUVIN 1130 3.5 3.5
DDBSA solution 1.0 5.0
FC 430 solution 0.1 2.0
diisopropanol amine solution -- 3.2
n-methyl-2-pyrrolidone -- 5.0
isopropanol -- 5.0
water -- 58.1
Example 11
A clear film-forming composition was prepared by mixing together the
following ingredients:
Solid weight
Ingredient in grams Solution weight in grams
carbamate functional 70.0 172.8
acrylic latex of Example M
CYMEL 303 30.0 30.0
TINUVIN 1130 3.5 3.5
p-TSA solution.sup.1 1.0 5.0
diisopropanol amine solution -- 3.5
isopropanol -- 50.0
water -- 17.3
.sup.1 20 weight percent solution of para-toluene sulfonic acid neutralized
with diisopropanol amine in water.
Example 12
A clear film-forming composition was prepared by mixing together the
following ingredients:
Solid weight
Ingredient in grams Solution weight in grams
hydroxyl functional 70.0 174.2
acrylic latex of Example N
CYMEL 303 30.0 30.0
TINUVIN 1130 3.5 3.5
p-TSA solution 1.0 5.0
diisopropanol amine solution -- 3.5
isopropanol -- 50.0
water -- 16.3
The film-forming compositions of Examples 7-12 were applied to a pigmented
basecoat to form color-plus-clear composite coatings over electrocoated
steel substrates. The pigmented basecoat for Examples 7-12 is commercially
available from PPG Industries, Inc. and identified as BWB-8555. The
basecoat was pigmented black in color. The electrocoat used on the steel
is commercially available from PPG Industries, Inc. and is identified as
ED-11.
The basecoat was spray applied in two coats to electrocoated steel panels
at a temperature of about 75.degree. F. (24.degree. C.) and a relative
humidity of about 60%. A ninety second flash time was allowed between the
two basecoat applications. After the second basecoat application, a
prebake time of approximately five minutes was allowed at 250.degree. F.
(121.degree. C.) before the application of the clear coating composition.
The clear coating compositions of Examples 7-12 were each applied to a
basecoated panel in two coats with a ninety second flash at 75.degree. F.
(24.degree. C.) allowed between coats. The composite coating was allowed
to air flash at 75.degree. F. (24.degree. C.) for ten to fifteen minutes
and to flash at 140.degree. F. (60.degree. C.) for ten to fifteen minutes
before baking at 285.degree. F. (141.degree. C.) for 30 minutes to cure
both the basecoat and clearcoat. The panels were baked in a horizontal
position. The properties of the composite coatings are reported in Table
II below.
TABLE II
Example Acid Etch Rating
7 3
8 3
9 2
10 5
11 5
12 9
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